Defensible space refers to that area between a house and an oncoming wildfire where the vegetation has been modified to reduce the wildfire threat and to provide an opportunity for firefighters to effectively defend the house. Sometimes, a defensible space is simply a homeowner’s properly maintained backyard.

Many people do not view the plants growing on their property as a threat. But in terms of wildfire, what is growing adjacent to their homes can have considerable influence upon the survivability of their houses. All vegetation, including native plants and ornamental plants in the residential landscape, is potential wildfire fuel. If vegetation is properly modified and maintained a wildfire can be slowed, the length of the flames shortened, and the amount of heat reduced, all of which assist firefighters to defend the home against an oncoming wildfire.

• The objective of defensible space is to reduce the wildfire threat to a home by changing the characteristics of the adjacent vegetation by: Increasing the moisture content of vegetation
• Decreasing the amount of flammable vegetation
• Shortening plant height Altering the arrangement of plants.

This is accomplished through the “Three R’s of Defensible Space” - see image below.

There are basically Three R's in he modification of fuels or vegetation for defensible space:

Removal: This technique involves trees and shrubs from the site. Examples of removal would be the cutting down of a dead tree or the cutting out of a flammable shrub.

Reduction: The removal of plants parts, such as branches or leaves would consitute reduction. Examples of reduction modification on are pruning wood from a shrub, removing low tree branches, and mowing dried grass.

Replacement: Replacement is the substitution of less flammable plants for more hazardous vegetation. For example removal of a dense stand of flammable shrubs and planting an irrigated well maintained flower bed would be a type of replacement modification.

Under the Defensible Space Law, vegetation must be cleared a minimum of 30 feet around houses and other structures. However, if the structure is on a slope or in tall trees (as in the diagram above) with a 40-percent slope uphill and side clearances of 150 feet and downhill clearance - the direction from which the fire will most likely come - of 200 feet are required. The defensible space requirements will vary with slope and type of wildland vegetation growing near the home.

For the most part, creating a defensible space employs routine gardening and landscape maintenance practices such as pruning, mowing, weeding, plant removal, appropriate plant selection and irrigation. For information on plant selection and placement go to the Living with Fire website at http://www.extension.unr.edu/Fire/firescape.hmtl. To obtain a copy of “Living with Fire: A Guide for the Homeowner” contact Ron Barrett, University of California Cooperative Extension at (775) 861-6501.

Inside this edition:
Call for Associate Director
Wildfires - Impacts on Watersheds
Defensible Space
Farm Bill 2002

pg. 2
pg. 3
pg. 4
pg. 5

to page 5